JP2002274014A - Coating composition for ink jet recording medium and ink jet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating composition for an ink jet recording medium capable of improving a gloss while maintaining rapid ink permeability to an ink acceptive layer having a casting layer coating agent, improving a weather resistance, and imparting sufficient followability to a stress change due to folding. SOLUTION: The coating composition for the ink jet recording medium comprises a synthetic resin emulsion having two or more different glass transition points (Tg) and emulsion polymerizing a radical polymerizable unsaturated monomer (A) having a silyl group and copolymerizable another radical polymerizable unsaturated monomer (B) in the presence of a radical polymerizable surfactant, and a colloidal silica. The ink jet recording medium is obtained by coating such a coating composition for the ink jet recording medium thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for a recording medium used in ink jet printing for high gloss photographic images, and more particularly to a coating composition formed to impart gloss to an ink fixing layer. A coating composition used for a cast layer. The present invention also relates to an inkjet recording medium coated with such a coating composition. The ink jet recording medium coated with the composition of the present invention is excellent in that it has high gloss, weather resistance, ability to follow a change in stress due to bending, and high ink receptivity.

[0002]

2. Description of the Related Art Printing by an ink jet printer is
It has grown rapidly these days because it is easy to enjoy high-definition images. Glossy paper or non-glossy paper is usually used for the ink-jet printing base material, and technological innovations are being made on each of them, and many patents have been filed accordingly. The image formation and fixing mechanism of an ink jet recording medium is generally such that an anionic ink is printed on a base material containing a cationic drug or pigment, and the ink is fixed by aggregation of an anionic component and a cationic component. . On glossy paper, the glossy layer applied on the ink fixing layer containing the cationic component has fine holes and cracks, and the ink penetrates to form an image by the action between the ink fixing layer below and the ink. Mostly, those that have been fixed are seen.

JP-A-7-149038 discloses a glass transition point (T) obtained by polymerizing a monomer having an ethylenically unsaturated bond.
g) A coating containing a pigment such as colloidal silica is applied to a polymer having a temperature of 40 ° C. or higher, and a surface gloss treatment is performed by cast coating at a temperature equal to or lower than the glass transition point in a state where the polymer does not completely form a film. It has been proposed to form a layer in a film formation failure state on a paper surface while maintaining gloss, thereby promoting ink penetration and carrying the ink to an ink fixing layer thereunder. However, in this case, since the glass transition point is higher than room temperature (40 ° C. or higher) and a film formation defect is actively caused, the glossy layer is very brittle, and if this inkjet paper is rolled or bent, There were problems such as numerous cracks in the glossy layer.

In Japanese Patent Application Laid-Open No. Hei 10-217601, an ink jet glossy layer is formed by using a water-soluble resin having relatively good film formation as an adhesive and mixing a large amount of pigment to deteriorate the film formation. Water-soluble resins have problems with water resistance, and can be freely used like monomers having ethylenically unsaturated bonds.
Since Tg cannot be changed, there have been problems such as a low degree of freedom in design, and the fact that the water-soluble resin has a low viscosity and is not suitable for high-concentration paint formulations.

[0005]

SUMMARY OF THE INVENTION Further improvement of gloss, which was insufficient, improvement of weather resistance, bending, while maintaining rapid ink permeability to the ink receiving layer of the prior art casting layer coating agent. It has been desired to obtain a coating composition capable of imparting sufficient followability to a change in stress due to aging.

[0006]

According to the present invention, a radically polymerizable unsaturated monomer having a silyl group (A) and another copolymerizable radically polymerizable unsaturated monomer (B) are reacted at a radically polymerizable interface. The above object can be solved by using a composition comprising a synthetic resin emulsion having two or more glass transition points and colloidal silica, which are simultaneously or separately emulsion-polymerized in the presence of an activator, in a gloss layer. I understood. In other words, by using a radical polymerizable surfactant during emulsion polymerization, the surfactant does not bleed out on the film surface, does not adversely affect ink permeability, and has a silyl group-containing radical polymerizable unsaturated. The scratch resistance of the film surface is improved by the copolymerizability of the monomer (A). Furthermore, a synthetic resin component having a high glass transition point that easily forms a discontinuous film allows a high ink permeability to be exhibited, and a synthetic resin component having a low Tg that produces a uniform film improves gloss,
In addition, the ability to follow a stress change due to bending can be improved, and the brittleness of the film can be improved.
Furthermore, the presence of colloidal silica can improve the ink receptivity while maintaining the transparency of the glossy layer. In general, a synthetic resin obtained by polymerizing a monomer having a radical polymerizable unsaturated bond has a plurality of Tg's that can be freely designed, an arbitrary temperature can be designed, and a polymerization reaction is performed under various conditions. A synthetic resin emulsion having a Tg curve having an inflection point can be obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a method for radical polymerization of a radically polymerizable unsaturated monomer (A) having a silyl group and another radically polymerizable unsaturated monomer (B) copolymerizable. Coating composition comprising colloidal silica and a synthetic resin emulsion having two or more different glass point transition points (Tg) obtained by emulsion polymerization in the presence of a surfactant, and for such an inkjet recording medium The present invention relates to an ink jet recording medium coated with a coating composition.

[0008] The synthetic resin emulsion constituting the coating composition of the present invention comprises a radically polymerizable unsaturated monomer (A) having a silyl group and another radically polymerizable unsaturated monomer (B) copolymerizable therewith. ) Are simultaneously or separately emulsion-polymerized in the presence of a radically polymerizable surfactant. Particularly, in the present invention, in order to produce a synthetic resin having two or more different glass transition points, two or more emulsion particles having different glass transition points, which are separately emulsion-polymerized, are mixed, or the polymerization is performed stepwise. It is necessary to use a multi-stage polymerization for changing the monomer composition or a so-called power feed polymerization for changing the monomer composition during polymerization as needed.

In the present invention, it is preferable to mix emulsion particles obtained by emulsion polymerization separately and to use an emulsion produced by multi-stage polymerization, since required physical properties can be exhibited in a well-balanced manner. .

Next, each component constituting the composition of the present invention will be described.

<Monomer Component> (A) Radical-Polymerizable Unsaturated Monomer Having Silyl Group The radical-polymerizable unsaturated monomer (A) having a silyl group of the present invention is obtained by hydrolysis of the silyl group. In addition to improving the scratch resistance of the film surface to take a crosslinked structure,
An effect of coupling a polymer with an inorganic component such as silicon can be expected, and in the present invention using colloidal silica,
The polymer and colloidal silica are chemically bonded to form a film that takes advantage of the characteristics of both inorganic and organic materials. Specifically, a flexible, water-resistant and heat-resistant film is formed.

The radically polymerizable unsaturated monomer having a silyl group (A) used in the present invention is represented by the following formula (1) or (2) having a radically polymerizable unsaturated bond. Compound. R-Si (X) ₃ (1) R-Si (R ′) (X) ₂ (2) In 1) and (2), R represents an organic group having a vinyl group, a (meth) acryloxy group, an epoxy group, a mercapto group, an amino group, an isocyanate group, or the like. R ′ represents a lower alkyl group having 1 to 3 carbon atoms.
X represents a methoxy group or an ethoxy group having a radical polymerizable unsaturated bond. Examples of the monomer having an alkoxysilyl group in the side chain include vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, and vinyl (2
-Methoxyethoxy) silane, vinylorganoalkoxysilane such as vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 3,4- Epoxyorganoalkoxysilanes such as epoxycyclohexylethyltrimethoxysilane, 3,4-epoxycyclohexylethyldimethoxysilane, mercaptoorganoalkoxysilanes such as γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-meta Acryloxypropyltriethoxysilane and the like can be mentioned. In the present invention, these unsaturated monomers (A) may be used alone or in combination of two or more. In the present invention, among these, from the viewpoint of polymerizability, it is particularly preferable to use vinyl triethoxy silane and 31-methacryloxypropyl triethoxy silane. The amount of the radically polymerizable unsaturated monomer having a silyl group (A) to be used is suitably from 0.1 to 15 parts by weight, preferably 0.1 to 15 parts by weight, based on all the radically polymerizable unsaturated monomers used. Is 0.5 to 10 parts by weight.

If the amount of the radically polymerizable unsaturated monomer having a silyl group is less than 0.1% by weight, complexing with colloidal silica becomes insufficient and water resistance may decrease. , More than 15% by weight may cause instability of polymerization, multiple generation of aggregates, increase in viscosity, and the like.

(B) Other copolymerizable radically polymerizable unsaturated monomer The other copolymerizable radically polymerizable unsaturated monomer (B) used in the present invention may be prepared by a conventional emulsion polymerization. If it can be used, it can be used without particular limitation.

These are composed of a main monomer (B-1), which is a main component of the synthetic resin, and a functional monomer (B-2) which modifies the synthetic resin to give a further function.

For example, as the main monomer (B-1), alkyl (meth) acrylate, cycloalkyl (meth) acrylate, olefin, vinyl ester, aromatic Group vinyl compounds and the like.

More specifically, alkyl (meth) acrylate and cycloalkyl (meth) acrylate include alkyl such as methyl, ethyl, n-butyl, t-butyl, propyl, 2-ethylhexyl and octyl. Examples thereof include alkyl (meth) acrylates having 1 to 12 carbon atoms, cyclohexyl acrylate, and cyclohexyl methacrylate.

Examples of olefins include ethylene, propylene, and vinyl esters such as vinyl acetate, vinyl esters of branched carboxylic acids, and vinyl laurate. Examples of aromatic vinyl compounds include styrene and α-methylstyrene. Can be

Further, the synthetic resin is modified to have storage stability,
Examples of the functional monomer (B-2) that imparts functions such as water resistance, chemical resistance, weather resistance, and adhesion include, for example, an ethylenically unsaturated carboxylic acid (B-) that improves storage stability and adhesion.
2a) a monomer (B-2b) having two or more radically polymerizable unsaturated bonds for improving water resistance, weather resistance, chemical resistance, adhesion, etc., an amide group, a nitrile group, a hydroxyl group, a glycidyl group, Methylol group, carbonyl group, fourth
Quaternary ammonium salts, ethylene oxide chains, and monomers having chlorine in the side chain (B-2 and others).

Ethylenically unsaturated carboxylic acid (B-2a)
Examples thereof include acrylic acid, methacrylic acid, crotonic acid, and maleic acid.

The monomers (B-2b) having two or more radically polymerizable unsaturated bonds include divinyl compounds, di (meth) acrylate compounds, tri (meth) acrylate compounds, tetra (meth) acrylate compounds, diallyl compounds , Triallyl compounds, tetraallyl compounds, and the like. More specifically, divinylbenzene, divinyl adipate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and polyethylene glycol (Meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,3-butyl di (meth) acryle DOO, trimethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth)
Acrylate, diallyl phthalate, triallyl dicyanurate, tetraallyloxyethane and the like can be mentioned. As other functional monomers (B-2 and others),
Examples of the monomer having a hydroxyl group include hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxybutyl methacrylate, and hydroxybutyl acrylate, and examples of the monomer having an amide group include acrylamide and methacryl. Amides and the like, monomers having a nitrile group include acrylonitrile and the like, and monomers having chlorine in the side chain include vinyl chloride and vinylidene chloride, and a monomer having a glycidyl group. Examples of the body include glycidyl methacrylate and glycidyl acrylate. Examples of the monomer having a methylol group include N-
Methylol acrylamide and the like, and the monomer having a carbonyl group include acetoacetoxyethyl methacrylate and the like.

In the present invention, as the main monomer of (B-1), alkyl (meth) acrylate, cycloalkyl (meth) acrylate, styrene, and vinyl ester of branched carboxylic acid are preferable. These may be used alone, but it is preferable to use a plurality of them in combination. For example, a combination of two or more alkyl (meth) acrylates and styrene, a combination of two or more alkyl (meth) acrylates, and a combination of a vinyl ester of a branched carboxylic acid and an askis methacrylate are water-resistant. , Weatherability, polymerization stability and the like. The use of a combination of two or more (meth) acrylic acid alkyl esters is convenient for adjusting the glass transition point and improving various physical properties.

Further, as the functional monomer of (B-2), an ethylenically unsaturated carboxylic acid is preferable, and this ethylenically unsaturated carboxylic acid is easily oriented on the surface of the synthetic resin emulsion particles. Partial neutralization forms an electric double layer and contributes to the dispersion stability of the emulsion particles.

As the above-mentioned component (B), at least one of them may be used, but alkyl (meth) acrylate, cycloalkyl (meth) acrylate, styrene and vinyl ester of branched carboxylic acid can be used. It is preferable to use a combination of at least one or more selected from at least one selected from ethylenically unsaturated carboxylic acids as the functional monomer. <Other components used during polymerization> Emulsion polymerization in the present invention is carried out in an aqueous medium with addition of other known components, and other components at this time include a surfactant and a polymerization initiator. Agent is used. In addition, a protective colloid, a chain transfer agent, a pH adjuster, an ultraviolet absorber, a photooxidant, and the like may be used if desired. The surfactant functions as an emulsifier at the time of emulsion polymerization, and specific examples thereof include ordinary anionic, cationic or nonionic surfactants. In the present invention, a radically polymerizable surfactant having one radically polymerizable unsaturated group in the molecule is particularly used. The radical polymerizable surfactant is chemically bonded to the polymer component due to the presence of the polymerizable unsaturated bond, and does not bleed out to the surface of the film as a free surfactant when the film is formed. This allows the ink to quickly penetrate into the fixing layer without causing bleeding in inkjet printing. When a radical polymerizable surfactant is not used, a free surfactant is present bleeding out on the film surface, and bleeding of the ink occurs during printing.

The radical polymerizable surfactant can be appropriately selected from known substances, and examples thereof include anionic and nonionic surfactants. Specific examples thereof include the following compounds 1) To 16).

[0026]

Embedded image

[0027]

Embedded image

[0028]

Embedded image

[0029]

Embedded image

[0030]

Embedded image

[0031]

Embedded image

[0032]

Embedded image

[0033]

Embedded image

[0034]

Embedded image

[0035]

Embedded image

[0036]

Embedded image

[0037]

Embedded image

[0038]

Embedded image

[0039]

Embedded image

[0040]

Embedded image

[0041]

Embedded image Further, in addition to the radically polymerizable surfactant, other surfactants such as an anion having no radically polymerizable unsaturated bond and a nonionic type can be used in combination. That is, examples of the anionic surfactant include sodium alkylbenzene sulfonate, sodium alkyl sulfonate, sodium polyoxyethylene alkyl ether sulfonate, and the like. Examples of the nonionic surfactant include a polyoxyethylene alkyl ether type, a polyoxyethylene alkyl ether type, a polyoxyethylene or a loxypropylene glycol type, and the like. These surfactants are charged in their entirety at the beginning of the polymerization, at least a part of them are dropped, mixed with a monomer and used as an emulsion monomer for the polymerization, or used in combination. In the present invention, from the viewpoints of polymerization stability and control of particle diameter, it is preferable to mix with a monomer and use it as an emulsion monomer for polymerization.

The total amount of the surfactant used is about 0.1 to 20% by weight based on all monomers. In particular, in the present invention, it is essential to use a radically polymerizable surfactant, but the amount of use is 0.3 to 10% by weight, preferably 0.5 to 5.0% by weight based on all monomers. %. If the amount of the radically polymerizable surfactant used is less than 0.3% by weight, the reaction system may aggregate or the reaction may not be completed. If used more than necessary, the surfactant is liberated on the surface of the coating layer to cause bleeding of the ink. If it exceeds 10% by weight, the viscosity of the reaction system may be too high or the water resistance may be reduced.

The polymerization initiator radically decomposes by heat or a reducing substance to promote addition polymerization of the monomer. Examples of the polymerization initiator include water-soluble or oil-soluble persulfates, peroxides and avizobis compounds. , For example, potassium persulfate,
Ammonium persulfate, t-butyl hydroperoxide, hydrogen peroxide, azobisisobutyronitrile (AIB
N), Rongalit, sodium metabisulfite, and the like. These may be used alone,
Two or more kinds may be used in combination. If desired, these polymerization initiators may be used in combination with a transition metal ion, and the transition metal ion is preferably ferric sulfate, cupric chloride, or ferric chloride. The protective colloid can be used without particular limitation as long as it is a known one used for emulsion polymerization, and examples thereof include polyvinyl alcohol and its derivatives, cellulose ether and its derivatives, starch derivatives and the like. You. The chain transfer agent is not particularly limited and may be appropriately selected from known ones.For example, alcohols such as methanol, ethanol, propanol and butanol, acetone, methyl ethyl ketone, cyclohexane, acetophenone, acetaldehyde, propionaldehyde, n- 2-8 carbon atoms such as butyraldehyde, furfural and benzaldehyde
Carboxylic acids, dodecyl mercaptan, lauryl mercaptan, normal mecaptan, thioglycolic acid,
And mercaptans such as octyl thioglycolate and thioglycerol. These may be used alone or in combination of two or more. Known pH adjusters include ammonia, sodium hydroxide, potassium hydroxide and the like. The UV absorber is not particularly limited, but may be a benzophenone derivative,
Benzotriazole derivatives are preferably used.
Some of these have a radical polymerizable unsaturated bond, and are preferred because they are copolymerized with the synthetic resin component. Hindered phenol-based and hindered piperidine-based photooxidants are preferably used,
As with the ultraviolet absorber, some photooxidants have a radical polymerizable unsaturated bond, and these are preferable because they are copolymerized with the synthetic resin component.

The present invention is characterized in that the synthetic resin emulsion obtained by emulsion polymerization has at least two or more glass transition points.

As for the glass transition point (Tg) of the polymer of the synthetic resin emulsion, at least one point is 30 ° C. or less, particularly -50 to 30 ° C., and at least another point is 30 ° C.
Higher, particularly preferably 100 ° C. or lower, and at least one point is -30 to 30 ° C.
More preferably, the point is between 50 and 90C.

When the glass transition point on the lower side is 30 ° C. or lower, not only is a uniform film obtained by drying to improve the gloss, but also, in actual use, the resin exhibits sufficient softness, Cracks in the coating layer on the surface can be suppressed. Also, the glass transition point on the high side
When the temperature is 30 ° C. or higher, microcracks are formed in the coating layer, and the ink is quickly transported to the ink receiving layer below through the cracks, so that the ink permeability is excellent. The resin component of the present invention can have the excellent properties of both components at the same time, and when combined with other requirements, provide a very excellent coating composition.

Here, the glass transition point refers to a temperature at which synthetic resin particles in a synthetic resin emulsion undergo a phase change from a hard and brittle glass state to a soft rubber state. The emulsion glass transition point in the present invention means that there are at least two or more phase change temperatures. To determine the glass transition point, use a differential scanning calorimeter (DSC)
By using an analyzer such as that described above, the presence of the inflection point can be easily confirmed.

In order to obtain a synthetic resin emulsion having two or more glass transition points according to the present invention, a synthetic resin emulsion which is separately emulsion-polymerized may be mixed, or a monomer composition in a polymerization step may be changed stepwise. It is necessary to use polymerization, a power feed polymerization method in which the monomer composition is changed as needed, and a seed polymerization method. The films of the synthetic resin emulsions obtained by these polymerization methods behave differently from synthetic resin emulsions prepared by homogenizing the monomer composition. In the case of a synthetic resin emulsion in which the monomer composition is homogenized and polymerized, the properties of each monomer when they are independently polymerized cancel each other, and a film having intermediate physical properties is obtained. Although this is useful in the application of synthetic resin emulsions, by specifying a polymerization method as in the present invention, a film having contradictory physical properties can be obtained. This is presumed to be due to the fact that the formed film is homogenized in the macro state, but has an inhomogeneous part in the micro state. In the present invention, it is preferable to mix synthetic resin emulsion particles which are separately polymerized, or to use a synthetic resin emulsion obtained by multi-stage polymerization.

When a synthetic resin emulsion is used as a mixture, for example, an acrylic ester copolymer emulsion or a styrene / acrylic ester copolymer emulsion having a glass transition point of 30 ° C. or lower and a glass transition point of 5
It is preferable to mix an acrylic ester copolymer emulsion or a styrene-acrylate ester emulsion at 0 ° C. or higher at a ratio of 10:90 to 90:10 (parts by weight) in terms of nonvolatile components.

When the synthetic resin emulsion of the present invention is obtained by a multi-stage polymerization method, for example, a monomer mainly composed of acrylic acid acrylate whose composition is adjusted so that the glass transition point is not higher than a desired temperature is emulsion-polymerized. Subsequently, it is preferable to carry out emulsion polymerization of a monomer mainly composed of acrylic acid acrylate whose composition has been changed so that the glass transition point becomes a desired temperature or higher. As a result, it is possible to form emulsion particles in a core-shell shape, a composite shape, a snow-like shape or the like. In this case, the ratio of the composition having a low glass transition point to the composition having a high glass transition point is 1 in terms of nonvolatile matter.
The ratio is preferably 0:90 to 90:10 (parts by weight). 1 resin component having low glass transition point
If the amount is less than 0 parts by weight, sufficient gloss cannot be obtained, and stress relaxation at the time of bending becomes insufficient. On the other hand, if the amount is more than 90 parts by weight, the film formation is too uniform, and the fine holes and cracks for absorbing the ink are insufficient, resulting in poor printability.

The present invention is characterized in that colloidal silica is used together with the synthetic resin emulsion.

Colloidal silica is an ultrafine silica sol which is dispersed in water in a colloidal state, and the primary particles generally have a particle size in the range of 5 to 100 nm.

In the present invention, commercially available colloidal silica may be used, may be surface-treated with a metal ion such as metaaluminate ion, may be monodispersed, or may have special particles. They may be connected in a rosary or branched and connected by processing.

Of these, those which have been surface-treated with metal ions such as metaaluminate ions are preferred because of their excellent miscibility.

The amount of colloidal silica to be used is as follows: synthetic resin emulsion: colloidal silica = 10: 90 to 90:10 in terms of nonvolatile content relative to the synthetic resin emulsion.
Is more preferable, and 30:70 to 70:30 is more preferable. <Other components to be added to the coating composition> The coating composition of the present invention may adjust or supplement whiteness, viscosity, fluidity, miscibility, preservability, weatherability, workability, etc. as necessary. For, various pigments, dyes, coloring pigment thickeners, pH adjusters, which can be used in aqueous coating compositions,
Surfactants, dispersants, defoamers, antifreezing agents, release agents, ultraviolet absorbers, photooxidants, and the like can be added.
An ink jet recording medium is obtained by applying the coating composition of the present invention as a gloss layer and drying. At this time, the material and structure of the substrate and the ink coating layer are not particularly limited as long as the substrate and the ink coating layer are generally used for an inkjet recording medium. For example, in order to impart gloss to a medium having an ink receiving function on a substrate such as paper, film or cloth, the gloss layer of the present invention is coated with a known coating method (comma coater, blade coater, air knife coater). Etc.), and perform a process of drying and imparting gloss.

In order to provide an ink receiving function by coating a base material with a composition comprising a pigment, a binder, a cationic substance having an ink fixing ability, etc., an ink fixing layer may be formed, or a paper or cloth may be used. Can be impregnated with a pigment, a binder, a cationic substance having an ink-fixing ability, or added at the papermaking stage, so that at least a part or all of them can be contained therein.

Examples of the pigment include zinc oxide, titanium oxide, calcium carbonate, silicic acid, silicate, clay, talc,
Mica, calcined clay, aluminum hydroxide, barium sulfate, lithopone, silica, colloidal silica and other inorganic pigments, polystyrene, polyethylene, polypropylene, epoxy resin, acrylic resin, acrylic-styrene copolymer, etc., spherical, hollow, or various Plastic pigments processed into various shapes and structures.

As the binder, polyvinyl alcohol, modified polyvinyl alcohol, starch and its derivatives, cellulose ether and its derivatives, sodium polyacrylate, polyvinylpyrrolidone, acrylamide copolymer, (meth) acrylic acid copolymer, polyethylene glycol, Polyvinyl acetate, polyurethane, urethane-acrylic copolymer, ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, styrene-butadiene-acrylic copolymer, glue, casein, Synthetic and natural polymers such as soy protein, gelatin, and sodium alginate can be used.

The coating amount (cast coating amount) of the gloss layer coating composition according to the present invention is 5 to 50.
g / m 2 (in terms of nonvolatile content) is preferred, and 7 to 35.
g / m2 (non-volatile content conversion) is more preferable.

As a method for drying and imparting gloss after coating, drying with warm air, calendering, casting and the like are used. More specifically, after coating, it is preferable to perform casting by setting the temperature of the cast roll to 60 to 100 ° C. while the coating composition is still wet.

The ink-jet recording medium thus obtained has extremely excellent performance in that it has high gloss, weather resistance, ability to follow a change in stress due to bending, and high ink receptivity. I have.

Example Production Example 1 70 parts by weight of water, 0.4 part by weight of sodium alkyl allyl sulfosuccinate and 0.2 part by weight of polyoxyethylene nonylphenyl ether were charged into a polymerization vessel, and dissolved by stirring. The polymerization reaction was allowed to proceed while dropping 10% by weight of 4% potassium persulfate and the following emulsified monomer composition over 2 hours. After dropping, the reaction was aged for 1 hour to give a milky synthetic resin emulsion. Obtained.

Water: 50 parts by weight Polyoxyethylene nonyl phenyl ether: 0.2 parts by weight Sodium alkyl allyl sulfosuccinate 1.0 parts by weight Methyl methacrylate 30 parts by weight Butyl acrylate 70 parts by weight Methacrylic acid 3 parts by weight Vinyltriethoxysilane 5 parts by weight 2 parts by weight of a 10% aqueous ammonia solution are added to this synthetic resin emulsion. The pH was adjusted to about 9. The glass transition point of the obtained synthetic resin emulsion particles was determined by DSC.
(Perkin-Elmer Co., Ltd.) showed an inflection point in a temperature range of 15 ° C. or lower.

Production Example 2-8 In Production Example 1, the emulsifier for the polymerization canister, the emulsifier in the emulsified monomer composition, the radically polymerizable unsaturated monomer, the monomer having an alkoxysilyl group in the side chain, and the like are shown in Table 1. Example 1 was carried out in the same manner as in Production Example 1 except for the change as shown in FIG.

[Table 1]

[Table 2]

Production Example 9 A polymerization vessel was charged with 50 parts by weight of water, 0.4 parts by weight of sodium alkyl allyl sulfosuccinate and 0.2 parts by weight of polyoxyethylene nonyl phenyl ether, dissolved by stirring, and heated to 75 ° C. The mixture was heated, and 13 parts by weight of 4% potassium persulfate and the following emulsified monomer composition were added dropwise over 3 hours to progress the polymerization reaction, thereby polymerizing the first stage.

Water 30 parts by weight Polyoxyethylene nonyl phenyl ether 0.5 parts by weight Sodium alkyl allyl sulfosuccinate 1.5 parts by weight Methyl methacrylate 30 parts by weight butyl acrylate 20 parts by weight Methacrylic acid 3 parts by weight 31-methacryloxypropyl tri 2 parts by weight of ethoxysilane Subsequently, the following emulsified monomer and 4% potassium persulfate 1
3 parts by weight were added dropwise over 3 hours to carry out the second stage polymerization.

Water 30 parts by weight Polyoxyethylene nonyl phenyl ether 0.5 parts by weight Sodium alkyl allyl sulfosuccinate 1.5 parts by weight Styrene 30 parts by weight Methyl methacrylate 15 parts by weight 2-ethylhexyl acrylate 5 parts by weight Methacrylic acid 3 parts by weight 3 2 parts by weight of 1-methacryloxypropyltriethoxysilane After dropping, the mixture was aged for 1 hour to obtain a uniform and good synthetic resin emulsion. The glass transition point of the obtained emulsion was measured by DSC. As a result, two inflection points were observed, one point in a temperature region of 15 ° C. or lower and one point in a temperature region of 70 ° C. or higher. Production Example 10 A polymerization vessel was charged with 50 parts by weight of water, 0.4 part by weight of sodium alkyl allyl sulfosuccinate and 0.2 part by weight of polyoxyethylene nonyl phenyl ether, dissolved by stirring, and heated to 75 ° C. The polymerization reaction was allowed to proceed while 3 parts by weight of 4% potassium persulfate and the following emulsified monomer composition were added dropwise over 3 hours to carry out the first-stage polymerization.

Water 30 parts by weight Polyoxyethylene nonyl phenyl ether 0.5 parts by weight Sodium alkyl allyl sulfosuccinate 1.5 parts by weight Styrene 45 parts by weight Methyl methacrylate 23 parts by weight 2-ethylhexyl acrylate 7 parts by weight Methacrylic acid 3 parts by weight 3 2 parts by weight of monomethacryloxypropyltriethoxysilane Subsequently, the following emulsified monomer and 4% potassium persulfate 1
3 parts by weight were added dropwise over 3 hours to carry out the second stage polymerization.

Water 30 parts by weight Polyoxyethylene nonylphenyl ether 0.5 parts by weight Sodium alkyl allyl sulfosuccinate 1.5 parts by weight Methyl methacrylate 18 parts by weight butyl acrylate 12 parts by weight Methacrylic acid 3 parts by weight 31-methacryloxypropyl tri 2 parts by weight of ethoxysilane After dropping, aging was performed for 1 hour to obtain a uniform and good synthetic resin emulsion. The glass transition point of the obtained emulsion was measured by DSC. As a result, one inflection point was found in a temperature region of 15 ° C. or lower, and one inflection point was found in a temperature region of 70 ° C. or higher.

Comparative Production Example 1-6 In Production Example 1, the emulsifier in the polymerization canister, the emulsifier in the emulsified monomer composition, the radically polymerizable unsaturated monomer, the monomer having an alkoxysilyl group in the side chain, and the like are shown. The same procedure as in Production Example 1 was carried out except that the composition was changed as shown in -2.

[Table 3]

Example 1 30 parts by weight of the synthetic resin emulsion of Production Example 1 in terms of nonvolatile content, and 7 parts by weight of the synthetic resin emulsion of Production Example 3 in terms of nonvolatile content
0 parts by weight were mixed, and the glass transition point of the obtained synthetic resin emulsion was measured by DSC.
Two inflection points were observed, one point in the following temperature range and one point in the temperature range of 70 ° C. or higher. A coating composition comprising 5 parts by weight of a thickener and 2 parts by weight of a polyethylene wax as a mold release agent was prepared by compounding 120 parts by weight of a non-volatile content with 100 parts by weight of a nonvolatile content of the above synthetic resin emulsion. .

This coating liquid is coated on a paper substrate with an ink fixing layer composed of a pigment, a binder, and a cationic substance, and the upper layer is coated with a bar coater. It was pressed against a cast drum having a mirror surface, dried, and then released to obtain a glossy inkjet recording paper. The cast coating amount at this time was 10 g /
It was m ^2.

Example 2-10 In Example 1, the type and amount of the synthetic resin emulsion,
The procedure was performed in the same manner as in Example 1 except that the amount of colloidal silica was changed as shown in Table 3. Evaluation Each glossy inkjet recording paper obtained in this way was evaluated for white paper gloss, printability and bending resistance, and the results are shown in Table 1. Details of each test are as follows. Gloss on white paper: Gloss at 75 ° was measured according to JIS-P8142 and evaluated according to the following criteria.

◎: 65 or more ○: 60 or more and less than 65 Δ: 55 or more and less than 60 ×: 55 or less Printability: Ink jet printing (ISO / JIS-SCID) using an ink jet printer PM-770 manufactured by Seiko Epson Corporation. JIS X9201-199
5: N5), and the printability was visually evaluated. The evaluation criteria were as follows.

◎: Printed well ○: Printed without problems △: Slightly adjacent inks were mixed ×: Inks flowed and mixed, making it impractical Bending resistance: obtained 90 inkjet recording paper
° and the state of the surface when bent was evaluated by visual observation.

：: No cracks are observed. Δ: Slight cracks are observed, but there is no problem in practical use. X: Cracks are generated together with a crackling sound.

Folding print resistance: After a bending resistance test was performed, ink jet printing (ISO / JI) was performed using an ink jet printer used for printability.
S-SCID JIS X 9201-1995: N5), and the printability was visually evaluated. ：: Printing does not affect the image. Δ: Some image distortion is observed when printing is performed, but there is no practical problem. ×: A good image cannot be obtained even when printing is performed.

[Table 4]

[Table 5] Comparative Example 1 100 parts by weight of the synthetic resin emulsion of the synthetic resin of Production Example 1 and 120 parts by weight of the non-volatile content were combined with colloidal silica, and 5 parts by weight of a thickener and 2 parts by weight of a polyethylene wax as a release agent were used. A coating composition having a non-volatile content of 38% by weight was prepared.

This coating composition was applied in the same manner as in Example 1 to obtain an ink jet recording paper. At this time, the cast coating amount was 10 g / m ² in terms of nonvolatile components. Comparative Example 2-5 In Comparative Example 1, the type and amount of the synthetic resin emulsion,
Comparative Example 1 was conducted except that the amount of colloidal silica and the amount of colloidal silica were changed as shown in Table 4.

[Table 6]

Claims (10)

[Claims] 1. A radical polymerizable unsaturated monomer (A) having a silyl group and another radical polymerizable unsaturated monomer (B) copolymerizable in the presence of a radical polymerizable surfactant. A coating composition for an ink jet recording medium comprising a synthetic resin emulsion having two or more glass transition points obtained by emulsion polymerization simultaneously or separately and colloidal silica. 2. The synthetic resin emulsion has at least one glass transition point of 30 ° C. or lower and at least one other glass transition point is higher than 30 ° C.
4. The coating composition for an ink jet recording medium according to item 1. 3. The coating composition for an ink jet recording medium according to claim 1, wherein the synthetic resin emulsion comprises two or more emulsion particles having different glass transition points, which are separately emulsion-polymerized. 4. The coating composition for an ink jet recording medium according to claim 1, wherein the synthetic resin emulsion is produced by multi-stage polymerization. 5. The copolymerizable other radically polymerizable unsaturated monomer (B) as a main monomer is an alkyl (meth) acrylate, a cycloalkyl (meth) acrylate, styrene, or a branched carboxylic acid. 5. An ink jet recording medium according to claim 1, wherein the functional monomer is at least one selected from vinyl esters and the functional monomer is at least one selected from ethylenically unsaturated carboxylic acids. Coating composition. 6. The radical polymerizable unsaturated monomer having a silyl group (A) is used in an amount of 0.1 to 15 parts by weight, preferably 0 to 15 parts by weight, based on all the radical polymerizable unsaturated monomers used. The coating composition for an ink jet recording medium according to any one of claims 1 to 5, wherein the coating composition is 0.5 to 10 parts by weight. 7. The amount of the radically polymerizable surfactant used is 0.3 to 10% by weight, preferably 0.5 to 10% by weight, based on all monomers.
The coating composition for an ink jet recording medium according to any one of claims 1 to 6, wherein the amount is from 5.0 to 5.0% by weight. 8. The coating composition for an ink jet recording medium according to claim 1, wherein the blending ratio of the synthetic resin emulsion and the colloidal silica is from 10:90 to 90:10 in terms of nonvolatile matter. 9. The ink jet printer according to claim 1, wherein an ink fixing layer comprising a pigment, an adhesive, and a fixing agent is provided on at least one surface of the substrate, and the ink fixing layer is provided on at least one surface of the ink fixing layer. An inkjet recording medium formed by applying a recording medium coating composition. 10. An ink jet recording medium obtained by applying the coating composition for an ink jet recording medium according to any one of claims 1 to 8 on a substrate containing a pigment and a fixing agent.